Patients are assigned randomly to 1 of 6 possible sequences of product use. Patients complete 3 weeks of nightly product application (7 consecutive nights each of BufferGel, PRO 2000/5 Gel, and placebo gel) separated by a one-week washout between product-use periods. Patients apply the gel to the shaft and glans of the penis at bedtime, leave on for a minimum of 6 hours, and wash off the next morning. Patients maintain a diary of product application and removal, side effects, and use of other medications. Follow-up evaluations, including a genital exam and urine testing, are performed after each product-use and washout period. [AS PER AMENDMENT 08/20/01: Digital photographs will be taken of any observed abnormality or normal area that is needed for clinical decision making and/or documentation purposes.] In addition, adherence is assessed, the patient diary is reviewed, and product acceptability questionnaires are administered after each product-use period. Patients receive monetary compensation for participation.